How to redesign stacks for lead-free builds with Speedstack 
Application Note AP510 

This application note is written for Speedstack users who are...

...proficient with editing stackups in the Speedstack editor, and have libraries and filters set up. For assistance in setting filters / libraries please contact your local Polar office. (An autostack license is also required)

Redesigning a stack for lead-free build

A common challenge for PCB fabricators is taking an existing FR4 stack and redesigning it for lead-free builds. Speedstack  offers a powerful  solution to this tedious process.  The "remake stack with autostack" facility allows you to take an existing stack and realise it with a new set of materials.

In this example we change the core and prepreg materials from standard FR4 to material with a better high temperature performance for lead-free soldering, higher Tg, glass transition temperature, an increased decomposition temperature, Td and lower coefficient of thermal expansion, CTE. Speedstack 2008 can accomplish this task with a few mouse clicks. 

The graphic above illustrates the Speedstack documentation for an existing stack. 

Remaking the stack with AutoStack

To switch materials, with the stack loaded into the Stack Editor click the Remake Stack with AutoStack button.

Speedstack will display the Stack Data window with the current material filters selected:

With the appropriate library loaded and filters applied choose the Hi Tg Cores and Prepregs from the drop down filter lists:

and click the Generate Stacks button to rebuild the stack using the new materials. Speedstack regenerates the stack, replacing the current materials with the new. The reprocessed stack is shown below.

The above example uses filters to preselect the better performing materials this is just one application of the filters.  Occasionally the new materials will need some final fine tuning to get all the impedances in specification.  The CI Results tab in Speedstack 2009  V9_04 and up will summarize any structures that need revising.

Changing material suppliers

You will find the Remake Stack with AutoStack facility useful in many applications; for example, if you run out of materials from one supplier you can reprocess the stack with materials from a second source with only a few mouse clicks.

To learn more about Speedstack please contact one of the Polar representatives below: